Considering CNC machine tools for a cutting-type manufacture, it has been known to change tools either directly or by means of a tool holder insert in a receptacle body, for example, a spindle of the corresponding driving units, by means of automatic tool changing arrangements in order to achieve, in doing so, an appropriate flexibility in view of various machining tasks and in order to also be able to rapidly and accurately replace worn tools. In order to enable this tool changing operation and in order to ensure that, following the tool change, the required high machining accuracy is maintained, strict requirements exist regarding the interface between the tool or the tool holder insert and the receptacle body, said interface being referred to as the coupling point. In practice, in particular interfaces using a so-called conical/plane surface junction between two tool components have proven to be successful, two examples of these having been described in DE 148 910 A1 and in DE 102 19 600 C5. In these known interfaces, the receptacle body has a conical receiving bore that is circumscribed by a first plane surface that extends rectangularly with respect to the bore axis and into which a tool holder insert having a corresponding conically shaped projection or collet pin can be inserted. A second plane surface is provided on the projection or the collet pin, said plane surface circumscribing said projection or collet pin and extending at a right angle relative to the projection or collet pin axis, while the cone angles of the receiving bore and the projection or collet pin are almost approximately the same. Both the conical receiving bore and the conical projection or collet pin of the tool holder insert are configured so as to open, i.e., widen, toward the tool side, thus enabling an easy installation of the tool holder insert on the receptacle body at the interface.
However, the quality of the connection between the tool holder insert and the receptacle body at the interface significantly depends on the degree of cleanliness at the interface. Even minimal amounts of contaminants that potentially reach the cone surface of the receiving bore or that enter between the plane surfaces of the receptacle body and the tool holder insert during a tool change, for example, can lead to considerable concentricity inaccuracies of the tool when the tool holder insert is mounted in the receptacle body. Consequently, automatic tool changing systems, as a rule, comprise special measures to keep the interface clean during a tool change, such measures including, for example, rinsing of the receiving bore and the tool holder insert before and after the tool change.
When a manual tool change is performed, keeping the interface clean is substantially more problematic because foreign bodies of contaminants can be detected by the naked eye only up to a certain size, and keeping the interface clean is ultimately dependent on the operator.
Furthermore, under extremely confined space conditions as exist, for example, with NC-controlled lathes comprising pivotable tool carriers, clamping of the tool holder inserts in the conical receiving bores is difficult. A clamping from the rear side of the tool holder insert facing away from the tool, for example by means of a threaded spindle inserted in the receptacle body, is not possible in the case of turret disks, for example.